The purpose of this activity is for students to continue to explore teen numbers as 1 ten and some ones, using a new version of a familiar tool, the double 10-frame. Students choose a teen number and build it. As they build teen numbers, students should notice that every teen number has a completed 10-frame, or 1 ten, in common. This further solidifies student understanding that all teen numbers have 1 ten.

Some students may build the teen number, counter by counter, each time. These students are still developing an understanding of 10 ones as 1 ten. Some students may realize that one of the 10-frames is always completely filled and only change the ones. When students notice the relationship between teen numbers and the 10 + n pattern, they look for and make use of structure (MP7). Students who leave one 10-frame full and change the counters in the other 10-frame are observing regularity in how the teen numbers are formed (MP8).

Double 10-frames are provided as a blackline master. Students will continue to use these throughout the year. Consider copying them on cardstock or laminating them and keeping them organized to be used repeatedly.

• “What was the same about the way you built the teen numbers? What was different?” (There was always one 10-frame that was full and some more in the next 10-frame. There was a ten. The amount in the second 10-frame was different.)
• “What is the same about the equations you wrote? What is different?” (There’s a 10 in each equation. Each show adding. The totals are all teen numbers. The totals are different. The number added to 10 is different.)

The purpose of this activity is for students to determine the value that makes an addition equation true. The numbers in the equations all use the relationship between 1 ten and some ones and teen numbers. Students find the value that makes the equation true with one addend or the total unknown. This will help when students solve story problems with the unknown value in different positions in a later lesson.

• “How are the last two problems related?” (They both show that 13 is the same as 10 and 3. 13 is the sum but they have different unknown values.)